Monocular is also compact, lightweight and easy to use. A monocular of the same magnification as the binocular can be half the weight of the binocular. They are also cheaper and easy to carry in public.
A binocular worth the money turn out to be the best for birding for obvious reasons. They are pretty easy to use and can support extended periods of birding without fatigue. The fact that you get a wide field of view and view with both eyes makes them a great choice.